The present invention relates to a multistage compression type rotary compressor in which an intermediate pressure refrigerant gas compressed by a first rotary compression element and discharged therefrom is sucked in a second rotary compression element, compressed and then discharged therefrom.
In this type of multistage compression type rotary compressor such as a high inner pressure type multistage compression rotary compressor, there has heretofore been a constitution in which a refrigerant gas is sucked in a low pressure chamber side of a cylinder from a suction port of a first rotary compression element, compressed by operations of a roller and a vane to obtain an intermediate pressure, and discharged from a high pressure chamber side of the cylinder to a discharge muffling chamber through a discharge port. Moreover, the intermediate pressure refrigerant gas discharged to the discharge muffling chamber is sucked in the low pressure chamber side of the cylinder from a suction port of the second rotary compression element, secondarily compressed by operations of a roller and a vane to constitute a high-temperature high-pressure refrigerant gas, and discharged into a sealed vessel from the high pressure chamber side through the discharge port and the discharge muffling chamber. Subsequently, the gas is discharged from the rotary compressor (see, e.g., Japanese Patent Application Laid-Open No. 2004-27970).
Each vane is movably inserted into a guide grove disposed in a radial direction of the cylinder, and a back pressure chamber (a storage portion) is constituted behind each vane. The intermediate pressure which is a pressure of the first rotary compression element on a refrigerant discharge side is applied to the back pressure chamber of the first rotary compression element, and the high pressure of the sealed vessel is applied to the back pressure chamber of the second rotary compression element. Moreover, the vane of the first rotary compression element is urged toward a roller side by a spring disposed in the back pressure chamber behind the vane and the intermediate pressure applied to the back pressure chamber. The vane of the second rotary compression element is urged toward a roller side by a spring disposed in the back pressure chamber behind the vane and the high pressure applied to the back pressure chamber.
Moreover, an intermediate inner pressure type multistage compression rotary compressor has a constitution in which a refrigerant gas is sucked in a low pressure chamber side of a cylinder from a suction port of a first rotary compression element, compressed by operations of a roller and a vane to obtain an intermediate pressure, and discharged into a sealed vessel from a high pressure chamber side of the cylinder through a discharge port and a discharge muffling chamber. Moreover, the intermediate pressure refrigerant in this sealed vessel is sucked in the low pressure chamber side of the cylinder from a suction port of a second rotary compression element, secondarily compressed by operations of a roller and a vane to constitute a high-temperature high-pressure refrigerant gas, and discharged from the high pressure chamber side through the discharge port and the discharge muffling chamber.
Each vane is movably inserted into a guide grove disposed in a radial direction of the cylinder, and a back pressure chamber (a storage portion) is constituted behind each vane. The intermediate pressure of the sealed vessel is applied to the back pressure chamber of the first rotary compression element, and the high pressure which is the pressure of a refrigerant discharge side of the second rotary compression element is applied to the back pressure chamber of the second rotary compression element. Moreover, the vane of the first rotary compression element is urged toward a roller side by a spring disposed in the back pressure chamber behind the vane and the intermediate pressure applied to the back pressure chamber. The vane of the second rotary compression element is urged toward a roller side by a spring disposed in the back pressure chamber behind the vane and the high pressure applied to the back pressure chamber (see, e.g., Japanese Patent Application Laid-Open No. 2003-172280).
In addition, in such a multistage compression type rotary compressor, a problem has been generated that a so-called pressure reverse phenomenon occurs in which a discharge pressure (the intermediate pressure) of the first rotary compression element and a discharge pressure (the high pressure) of the second rotary compression element are reversed. There is a possibility that the reverse phenomenon of the pressure occurs in a situation in which a refrigerant can sufficiently be compressed by an only compression work in the first rotary compression element at a time when the rotary compressor has a light load. In this case, since the compression work is not substantially performed in the second rotary compression element, the pressure decreases owing to a circulation resistance or the like in a process in which the refrigerant discharged from the first rotary compression element flows through the second rotary compression element on a discharge side. Therefore, the discharge side pressure of the second rotary compression element becomes lower than that of the first rotary compression element.
Moreover, in a case where an evaporation temperature of the refrigerant rises at a high outside air temperature, a suction pressure of the first rotary compression element rises. In consequence, the discharge pressure of the first rotary compression element also rises. On the other hand, the discharge pressure (the high pressure) of the second rotary compression element is regulated so that the pressure does not rise above a pressure set beforehand in accordance with the number of rotations or the like. Therefore, in a case where the intermediate pressure as the discharge pressure of the first rotary compression element rises in this manner, pressure reversal sometimes occurs in which the intermediate pressure and the high pressure are reversed.
When the discharge pressure of the first rotary compression element and the discharge pressure of the second rotary compression element are reversed in this manner, the pressure in the cylinder of the second rotary compression element (the pressure (the intermediate pressure) of the refrigerant sucked in the second rotary compression element) rises above the discharge pressure (the high pressure) of the second rotary compression element applied as a back pressure of the vane. Therefore, a problem has occurred that an urging force to urge the vane toward the roller is eliminated, vane fly of the second rotary compression element occurs, a noise is made and an operation of the second rotary compression element also becomes unstable.
Furthermore, even in a case where the above-described pressure reverse phenomenon does not occur, when the discharge pressure of the first rotary compression element becomes substantially equal to that of the second rotary compression element, the urging force to urge the vane toward the roller decreases. Therefore, the vane fly sometimes occurs in accordance with an operation situation (during transition or the like).
In addition, there has also been a disadvantage that once the vane fly occurs, much time is required until the vane follows the roller, that is, the vane fly is eliminated.